Abstract: Recently our research group published a paper in JAMA which showed that after Roux-en-Y gastric bypass surgery (RYGB), patients are at significantly increased risk for developing an alcohol use disorder. Several lines of research are consistent with this finding: 1) anecdotal information from RYGB patients suggests that they become intoxicated much more quickly, 2) there are numerous reports of automobile accidents that have resulted from RYGB patients driving while intoxicated after drinking a small amount of alcohol, and 3) the pharmacokinetics of alcohol change considerably after RYGB. The pharmacokinetic changes are of considerable interest to us as they likely lead to significant impairments and changes in reinforcement. These changes may serve as a potential causal mechanism for the subsequent development of an alcohol use disorder. In the current study we propose to investigate RYGB patients with a prospective, longitudinal design. We will examine cognitive and driving impairment after surgery as well as study the changes in reinforcement that may occur in RYGB patients. Finally, we aim to better characterize the changes that occur in the pharmacokinetics of alcohol following bariatric surgery and examine key variables which may play a role in the development in alcohol use disorders.